Method of making grid bearings



June 10, 1952 A. w. scHLucHTER 2,599,726

METHOD OF' MAKING GRID BEARINGS Original Filed April l1, 147

Patented June 10, 1952 Alfrezlvfw." Schluchter; T'Dearborn;`

Thisyinvention -lh'astd'ldowith- 'grid 'bearingsy of thetypefdescribeeandwc1aimed inmypriorappli;

cation; rSerialir-No. `342,061.;milled` June 24,V 1940, r. now abandcned,t"andwvith methodsfofsmakingfthe samen: This; is;` v-awdiyisionl oi';v my r-'prior applica' tion Serial. Noa-17403582; ledl Apri1.11,f1947..

Gridf-bearngsaare :characterized by bearingV t surfaceslconsistmgbf a multiplicity of smallareas of fhardvrande= softbearing metals arranged f in a1te1-nating.r rrsuccessionW:icircumferentially,- andi: preierablyi falso' ,-transversolas'iJ4 of -the shaft.v `The vhardunetal 'fia-usually yuni-tedwxivlth a .strong supporting. backtoenablethe bearingtolcarry.heavyl y loadss: Thislload-bearing-i structure isiA referred `vto as `the,-grdor..n1atrix.-Flhelareasof soft rnetal', H15 preferably.lead,tin on le'adalloy;` arefwell bonded i to v-thematrixa and-givetheibearingdesirableiric- Y tionalpropertiesnasiwellas `embeddability. As pointed out in said prior application, it is neces-r sarmin orderto obtain superior performance with 20 thistypeof baringfto have thefalternatingareas of softbearingimetal spaced from. each `other not more than. approximately.070'` center rto center measured1,circumeifentially.M of the :bearing: While gridbearingstofllner pattern will support f heavy loads/and afford -longenlifefin the case of the nestl patterns, fon example,-4 xpatterns `hav ing4 spacingsof. .012.2 or fless; manufacture is dif\ cultibecause .the npi-ts or depressions arenecessarily quite shallow and impose closer tolerances 30 on machining oper-ationsr The gridwmay have various-configurations as disclosed-1in' saidprior applieationmy In 'one `form the pits for depressions consistait `ilnegrooxxes extending 4tran'sversely: of therbearing: w In` :'anothereembodiment" the maf tnx-may befprovidedfwithipizojections'exposed at the l bearing: surface, :to take,` efthe load"` and i sur-1. rounded by soft bearing metalen'Apreferredform T2 consistsiof atmatrlx having:a-'multiplicityi'ofrsmall circmnferennanynander-transversely?spacieuxpi'tsz40 orrdepressions;

I have?foun'drIthatzpuref aluminumsfisl an Sexcellent'amateriakfromwhiblrItoimake thegridlbrf. matrix: "zfHowever: wherheavierloadsfare to be' f bornettwillbesioundmreferablelto:employfthardhrx45 enable aluminumtaflloysg'havlng considerable Icom-1L pressivezstrength-gnrfheialuminumzfor;aluminum alloy-:sisi preferablywdnzftheformzofra relatively'l f thin: layeri .orsfcoating -bon'dedztox` 'asteelz :lbac'lcto i ffincreaseethedoaidscarrylng;capacit The'fphrase aluminum vlaasezfmeta "iris Ausecliirntlretitollowrin' dess1-ipticrmamdclairxisitoclncmdebothiIllllialuf:r minumfandzraluminunn zalloys. as f myvsimproved' process:mawbeusedwitheither 55 I prefereto:employ:in-ztlreinitsSoridepressions2L:V

2 anwA alloy :oflead which isV resistantgfto corrosion@ Lead may berenderedresistantfto corrosionbr the addition of .tin and/or antimon-y. `Iridium also serves thispurposebutisvery costly; Bearings lof l the ftype herein` disclosed arei-esp'eciall;4 subject" tocorrosion which proceedslinwardlir along-.th bond between the-lead alloy and" 'the aluxn'iriur'n i basevmetalwand-is produced -by theiei'enctsfof the atmosphere,:moisture or `acid lubricating .olsl Antimony .seernsto be Inre' effective than tinin" inhibitingthis.typelof corrosion? Where an all tin bath is employed it is not necessary to use a special dcoxidizer as the tin will form a good bond with the aluminum base metal and the bond will not be subject to corrosion. While tin will suffice for the initial coating of the strip it will not be found satisfactory for the final filling of the pits or depressions of bearings for use at high speeds and heavy loads where high operating temperatures are involved as it has undesirable frictional properties and a low melting point.

I prefer to employ for this bath either pure tin or an alloy of lead and tincontaining at least 30% tin to insure against corrosion. The composition 50% lead and 50% tin is particularly desirable because of its low melting temperature. It is estimated that the amount of calcium that can be held in solution in a lead or lead alloy bath at the low temperatures employed will not exceed from 1/4E% to 1/2%. For best results sufficient calcium should be added to the bath from time to time to maintain this proportion.

While the strip is thus submerged in the bath I lightly abrade the aluminum base metal surface preferably by brushing it with a wire brush. Brushing removes some of the oxide coating as well as some of the metal from the surface of the matrix. The particles of aluminum base metal assist in deoxidizing the bath. The cleaning and initial coating of the strip is preferably done in a separate bath to avoid the possibility of particles of aluminum base metal or aluminum oxide becoming embedded in the knurling roller used in the next step of the process and interfering with its operation.

After the strip has thus been given a protective coating of soft metal it is removed from the first bath and, preferably while the coating is still molten, the strip is submerged in a bath of leadtin alloy of any desired composition as described in connection with the first bath, preferably one containing at least 30% tin to prevent corrosion, and, of course, the same small addition as before of an alkaline earth deoxidizer, preferably calcium. The strip, while submerged, is operated on by a knurling roller which forms pits or depressions in the aluminum base Ametal surface and also agitates the molten metal to insure replacement of the initial coating by the metal of the second bath. Where the strip consists wholly of aluminum or aluminum alloy the pressure of the knurling roller tends to cause the molten metal to adhere to the back although there is no objectionable adherence where a steel back is used. The preferred lead-tin alloy mentioned above is particularly desirable where the back is of aluminum or aluminum alloy because it has a long freezing range during which adhering metal may be readily removed after the strip is taken from the bath.

The bath is preferably maintained at a temperature of about 535 F., this being sufficiently high to prevent freezing of the metal but sufficiently low sc that the bond is preserved and oxidation is reduced. At this temperature the coating of metal on the strip is sufficiently viscous so that it does not readily run off when the strip is removed from the bath. The strip is removed in substantially horizontal position to retain the new coating on the strip and it will be found that this coating forms a strong thermal-bond with the metal of thematrix.

The strip is thereafter immersed in a third bath of the alloy desired for the soft metal area of the bearing surface. The bond previously obtained may or may not be wholly dissolved in the third bath. To insure that most of the previous coating is removed from the pits or depressions and replaced by the alloy of the third bath, the blank may be agitated slightly in the bath or the molten metal itself may be agitated by means of a pump or the like. f

The composition of the final bath preferably consists of an alloy of lead, tin and antimony in the proportions of from 1A% to 5% antimony, 3% to 20% tin and the balance lead, together with a small amount of calcium. Where high bearing operating temperatures are involved it is preferable to reduce the tin content to from 5% to 10% of the total as tin lowers the melting point of the alloy. The preferred composition is 5% tin, 3% antimony and the balance lead, together with a small amount of calcium to insure a' good bond. Calcium forms compounds with both tin and antimony which rise to the surface as dross. It is estimated that the proportion of calcium which can be held in solution in the lead in this bath at the preferred operating temperature of 535 F.is but a few hundredths of 1% but it has been found to be essential in vorder to obtain a good bond. The lower limit of tin is determined by the minimum amount which will give a substantial degree of resistance to corrosion; the upper limit by the fact that further additions lower the melting point of the alloy so much as to render the bearings unsuitable for use where they are subjected to relatively high operating temperatures. Tin also reduces drossing of the lead. The relatively high lead content improves thefrictional properties of the alloy. Antimony greatly improves the resistance of the alloy to corrosion particularly in the region of the bond and also increases the hardness of the alloy.

If desired the third bath may be dispensed with and the above described tin-antimony-calciumlead alloy may be used in the bath in which the strip is knurled. The advantage of using a separate bath for the knurling operation is that with the antimony omitted much more calcium can be held in solution so that there is greater assurance of obtaining a good bond. However, I have been successful in obtaining a good bond employing as much as 3 antimony in the knurling bath.

It may also be feasible to employ but a single bath, preferably consisting of the above described antimony containing alloy, provided the knurling operation is screened or otherwise protected from particles of aluminum oxide or aluminum base metal resulting from the brushing operation which might lodge in the knurl and interfere with its operation.

It may be found satisfactory in some bearing applications to dispense with antimony in the final bath.A In such case on the order of at least 30% tin should be employed in the lead-tincalcium alloy to provide good resistance to corrosion. However, it is preferable to employ antimony as it is believed to be more effective in protecting the bond from corrosion.

The process above described may be carried out with matrix metal'in the form of iiat blanks of sufficient 'size to form one or more bearings. `Or the matrix metal may be formed to bearing shape before. However, for large production it will be found preferable to employ the well-known strip process in which a strip of the matrix metal is passed continuously through a bath or baths in which the foregoing operations Vare performed.

Af ter.dthez natrix 'metal` has been .thus knurledw and'coatedewith-softbearing Lmetal it `is removedfromfthebath-fand, if'in thelform of a strip or multiple blank, is cut to the length desired for the bearing. The bearing blanks are thereafter 5 formed toshape, vif this had not` been done before coating, and machined to exposethe alternate areas of soft bearing metal and metal of the matrix. In somecases `it -may be preferred not to carry the machining so far and leave a thinY overlay of softrbearing metal `over the entire` bearing. Surface. i

bond to the aluminum surface. The aluminum base metal grid.,which. enables the bearing to carry heavy loads, possessesgood bearing prop` erties,4 and is superior to` copper in this respect. The .corrosion resistant lead `alloy provides good frictional. properties and embedability In the drawings I have illustrated diagrammatically suitable apparatus for carrying out my process with the matrix metal in the form of a continuous strip, together with several embodiments of the resulting bearing.

In the drawings:

Figure l is a diagrammatic view showing the application of my process to the preparation of a continuous strip of bearing metal;

Figure 2 is a perspective view of one configuration of grid bearing in which my invention may be embodied;

Figure 3 is an enlarged, fragmentary view of a portion of Figure 2; and,

Figures 4 and 5 are views similar to Figure 3 showing modified grid patterns.

Referring to Figure l, I0 indicates a strip of aluminum base metal or, preferably, aluminum base metal bonded to a supporting strip of steel. le indicates the rst bath of molten lead, tin, or lead-tin alloy as described above through which the strip passes as shown in the drawings. At le there are illustrated revolving wire brushes which abrade the surface ofthe strip, thereby exposing a fresh, clean surface of aluminum base metal to contact with the molten metal.

The strip leaving bath I 4 passes into the second bath Il of the composition disclosed above. I8 indicates a revolving knurling roller submerged in the molten metal which gives the desired configuration to the aluminum base metal surface of the strip and at the same time agitates the metal of the bath.

Thereafter the strip passes into a similar bath 2a containing soft bearing metal of the composition described above as desired in the nal bearing. 22 indicates rollers which guide the strip and hold it submerged in the bath. In this bath the previous coating is dissolved and to insure that none remains in the pits or depressions, means, such as a suitable pump 2i), may be provided to agitate the molten metal.

The aluminum base metal grid or matrix is thus provided with a thermally bonded coating of substantially the same composition as the metal of the bath. Thereafter the composite strip may be formed to bearing shape as shown in Figure 1 and machined until the grid pattern is exposed as shown in Figure 2. The bearing shown in Figures 2 and 3 consists of a steel back 23 having a lining 24 of aluminum base metal knurled to form a multiplicity of pits or depressions 26 Which are filled to the level of the surrounding.metal.bycorrosion- `resistant-.lead alloy as described. e.

In @the `-mo zlincatien -shown-.in Figur-.e .4 the back-d8` consists onaluminumbase: metal, which is knurledorotherwiseformed .tol provide `a multiplicity of projections 31), f. the spaces. between whichaefilled Laith-soft, bearing metal l as described.

tendingtransversely-of` the` bearingand lled wi-thfsoftsbearing metal? l Bearings-made-V according to `this invention, having 48-pitsato thelinear i-nch,-have been subjected; to thorough testsunderVV heavy loads and at highspeedsffor-.long periodsof time and have f shown-little:wear1 Aluminum 4base metal pos-- sesses/advantages` over" silver, --Which has beenused-foru theimatrix-:metan-:because of its much .lower-cost@ 4Aluminum-basemetal is superior to copper-as a `bear-ingsurface and it is believed it `will likewiserbe found-.more economical to use.

Wherefthebearingload is not too heavy, economy may be effected by using hardenable aluminum strip without a steel back as this will make unnecessary the operation of cladding the steel strip with aluminum.

I claim:

1. In the method of making a gridded bearing in which a readily oxidizable metal bearing blank is immersed in molten soft bearing metal and, while so immersed, has surface oxidation removed therefrom by abrading and indentations formed therein to receive said soft bearing metal; the improvement which consists in including in said molten soft bearing metal a small but effective amount not greater than about 1/2% of an alkaline earth metal as a deoxidizer, whereby the abraded surface is maintained substantially free ,of oxides to thereby promote the adhesion of said soft bearing metal blank.

2. In the method of making a gridded bearing in which an aluminum base metal is immersed in molten soft bearing metal and, while so immersed, is abraded to remove surface oxidation and in which indentations are formed therein to receive said soft bearing metal, the improvement which consists in including in said molten soft bearing metal a small but effective amount not greater than 1A% of an alkaline earth metal as a deoxidizer to maintain the surface of said aluminum base metal substantially free of oxides and thereby promote the adhesion of said soft bearing metal to said aluminum base metal.

3. In the method of making a gridded bearing in which a readily oxidizable metal bearing blank 1s lmmersed in a melt of a soft bearing material of the class consisting of lead and lead base alloys and, while so immersed, is abraded to remove oxide films from its surface and has indentations formed therein to receive said bearing material, the improvement which consists in including in said melt a small but effective amount not greater than about 1/2% of an alkaline earth metal as a deoxidizer, whereby the abraded surface of said metal bearing blank is maintained substantially free of oxides to promote the adhesion of said soft bearing material to said metal bearing blank. v 4. In the method of making a gridded bearing in which a readily oxidizable metal bearing blank 1s immersed in a molten soft bearing metal and, while so immersed, is abraded to remove oxide nlm from its surface and has indentations formed 1n said surface to receive said soft bearing metal,

to said metal bearing the yimprovement which consists in including in said molten soft bearing material a small but effective amount not greater than about 1/2% of calcium as a deoxidizer. whereby the adjacent surfaces of said bearing blank and said soit bearing metal are maintained substantially free of metal oxides to thereby promote the adhesion of said soft bearing metal to said blank.

5. In the method of making a gridded bearing in which an aluminum base metal bearing blank is immersed in a melt of a soit bearing metal of the class consisting of lead and lead base alloys and, while so immersed, has a surface abraded to remove oxide lms therefrom and has indentations formed therein to receive said soft bearing metal, the improvement which consists in including in said melt a small but eieetive amount not greater than about 1/2% of calcium as a deoxodizer, whereby the abraded surface of said aluminum base metal bearing blank is maintained free of metal oxides to thereby promote adhesion of said soft bearing metal to said bearing blank.

6. The method as in claim 5 in which the lead base alloy consists of to 5% antimony, 3% to 20% tin, and the balance substantially all lead.

ALFRED W. SCHLUCHTER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,984,624 Bagley Dec. 18, 1934 2,264,251 Shoemaker Nov. 25, 1941 2,264,252 Shoemaker Nov. 25, 1941 2,288,635 Lyons July 7, 1942 2,364,503 Zink Dec. 5, 1944 2,446,996 Bouton Aug. 17, 1948 FOREIGN PATENTS Number Country Date 23,476 Great Britain 1892 536,414 Great Britain May 14, 1941 550,485 Great Britain Jan. 1l, 1948 

1. IN THE METHOD OF MAKING A GRIDDED BEARING IN WHICH A READILY OXIDIZABLE METAL BEARING BLANK IS IMMERSED IN MOLTEN SOFT BEARING METAL AND, WHILE SO IMMERSED, HAS SURFACE OXIDATION REMOVED THEREFROM BY ABRADING AND INDENTATIONS FORMED THEREIN TO RECEIVE SAID SOFT BEARING METAL; THE IMPROVEMENT WHICH CONSISTS IN INCLUDING IN SAID MOLTEN SOFT BEARING METAL A SMALL BUT EFFECTIVE AMOUNT NOT GREATER THAN ABOUT 1/2% OF AN ALKALINE EARTH METAL AS A DEXODIZER, WHEREBY THE ABRADED SURFACE IS MAINTAINED SUBSTANTIALLY FREE OF OXIDES TO THEREBY PROMOTE THE ADHESION OF SAID SOFT BEARING METAL TO SAID METAL BEARING BLANK. 